Marine lubricant

Abstract

The present invention relates to a cylinder lubricant having a BN, determined according to the ASTM D-2896 standard, of greater than or equal to 40 milligrams of potassium hydroxide per gram of lubricant, comprising a lubricant base oil for a marine engine and at least one overbased detergent that is based on alkali or alkaline-earth metals, and which also contains an amount of 0.01% to 10% by weight relative to the total weight of the lubricant, of one or more compounds (A) chosen from esters of saturated fatty monoacids comprising at least 14 carbon atoms and of alcohols comprising at most 6 carbon atoms.

What is claimed is: 
     
       1. A method for lubricating a two-stroke engine powered with any type of fuel oils, for which the sulfur content is less than 4.5% m/m said method comprising operating the engine with a single two-stroke cylinder lubricant having a BN determined according to the ASTM D-2896 standard, comprised in the range from 50 to 58 mg of KOH per gram of lubricant, and having a neutralization efficiency index superior or equal to 99, comprising a lubricant base oil for a marine engine and at least one overbased detergent based on alkaline or earth alkaline metals, wherein it further contains an amount of 0.01% to 10% by weight based on the total weight of the lubricant, of one or more compounds (A) selected from the group consisting of:
 mono-esters of saturated fatty mono-acids having from 14 to 22 carbon atoms and of mono-alcohols including at most 6 carbon atoms. 
 
     
     
       2. A method for lubricating a two-stroke engine powered alternatively with both fuels with a sulfur content of less than 1.5% m/m and fuels with a sulfur content of greater than 3% m/m, comprising operating the engine with a single two-stroke cylinder lubricant according  claim 1 . 
     
     
       3. A method for preventing corrosion and/or reducing the formation of deposits of insoluble metal salts in a two-stroke marine engine powered with a fuel oil for which the sulfur content is less than 4.5% m/m, said method comprising operating the engine with a single two-stroke cylinder lubricant having a BN determined according to the ASTM D-2896 standard, comprised in the range from 50 to 58 mg of KOH per gram of lubricant, and having a neutralization efficiency index superior or equal to 99, comprising a lubricant base oil for a marine engine and at least one overbased detergent based on alkaline or earth alkaline metals, wherein it further contains an amount of 0.01% to 10% by weight based on the total weight of the lubricant, of one or more compounds (A) selected from the group consisting of:
 mono-esters of saturated fatty mono-acids having from 14 to 22 carbon atoms and of mono-alcohols including at most 6 carbon atoms. 
 
     
     
       4. The method according to  claim 1 , wherein the sulfur content of fuel oils is comprised from 0.5% to 4% m/m. 
     
     
       5. A method for lubricating a two-stroke engine according to  claim 1  wherein the fatty acids are selected from myristic, pentadecylic, palmitic, margaric, stearic, nonadecylic, arachidic, heneicosanoic, behenic acids. 
     
     
       6. A method for lubricating a two-stroke engine according to  claim 1  wherein the alcohols are selected from ethanol, methanol, propanol and butanol. 
     
     
       7. A method for lubricating a two-stroke engine according to  claim 1  comprising from 0.1% to 2% by weight of compounds (A) based on the total weight of the lubricant. 
     
     
       8. A method for lubricating a two-stroke engine according to  claim 1  having a BN determined according to the ASTM D-2896 standard, comprised in the range from 54 to 56 mg of KOH per gram of lubricant. 
     
     
       9. A method for lubricating a two-stroke engine according to  claim 1  which comprises one or more functional additives selected from dispersant additives, anti-wear additives, anti-foam additives, anti-oxidant and/or anti-rust additives. 
     
     
       10. A method for lubricating a two-stroke engine according to  claim 1  which comprises at least one overbased detergent selected from the group formed by carboxylates, sulfonates, salicylates, naphthenates, phenates and mixed overbased detergents associating at least two of these types of detergents. 
     
     
       11. A method for lubricating a two-stroke engine according to  claim 1  which comprises at least 10% of one or more overbased detergent compounds. 
     
     
       12. A method for lubricating a two-stroke engine according to  claim 1  wherein the overbased detergents are compounds based on metals selected from the group consisting of calcium, magnesium, sodium and barium. 
     
     
       13. A method for lubricating a two-stroke engine according to  claim 1  wherein the detergents are overbased with insoluble metal salts selected from the group consisting of carbonates, hydroxides, oxalates, acetates, glutamates of alkaline and earth alkaline metals. 
     
     
       14. A method for lubricating a two-stroke engine according to  claim 1  wherein the overbased detergents are carbonates of alkaline or earth alkaline metals. 
     
     
       15. A method for lubricating a two-stroke engine according to  claim 1  wherein at least one of the detergents is overbased with calcium carbonate. 
     
     
       16. A method for lubricating a two-stroke engine according to  claim 1  which comprises at least 0.1% of a dispersant additive selected in the family of PIB succinimides.